This invention relates to drilling structures and, particularly, drilling structures wherein it is required that the working or equipment floor be elevated to a position above ground level.
For many drilling operations, such as when petroleum is to be extracted, it is necessary to drill relatively deep wells, thereby requiring longer drill strings and larger traveling blocks and hooks, all of which necessitate the use of greater mast heights. In order to accommodate the latter requirements for deep-well drilling, it is has become the custom to use an equipment floor on which are mounted drawworks and other drilling equipment which is elevated above ground level. For example, the equipment floor may need to be located as much as 25 feet or more above the ground. Such raised equipment floors are needed to provide clearance for relatively tall blow-out prevention apparatus.
In order to accommodate the need for an elevated equipment floor, numerous structures have evolved, but, in many respects, they have proven deficient. Most particularly, prior art elevated floor structures have proven to be relatively complex and time consuming to assemble at the drilling site, and, for this reason, are expensive to assemble and use. In many such prior art structures, the elevated floor and then the mast must be constructed and connected together in, essentially, a piece-by-piece operation, very often requiring the use of a crane which thereby increases the expense. Further, when such structures are finally erected, the rigging or outfitting of them must be carried out at the elevated level further requiring the use of a crane and enormously complicating the rigging process.
Examples of such prior art structures include those which have a relatively low substructure supporting a tall mast, and the elevated equipment floor is inserted in the mast at a given distance above ground level. Usually, an additional elevated support structure is provided for the drawworks. Quite clearly, in such an arrangement, the rigging operation must be carried out at an elevated level requiring the use of cranes and, prior to rigging being able to occur, it is necessary that separate raising operations be carried out for the various portions of the equipment floor. This arrangement, therefore, produces a complex arrangement for constructing the elevated floor, as well as an expesive rigging operation.
It is an object of this invention to provide a drilling structure having a mast and elevatable equipment floor which is relatively easy and inexpensive to assemble and rig.
Another object is to provide a drilling structure having an elevatable equipment floor, wherein the assembly can be fully rigged or outfitted at substantially ground level.
A further object of this invention is to provide a drilling structure having the capability of elevating the equipment floor utilizing hoist mechanisms which are a part of the drilling structure.
An additional object of this invention is to provide a drilling structure having an elevatable equipment floor on which a mast is raised and then the equipment floor, including the raised mast, is raised to the desired elevated position.
Still another object of this invention is to provide a drilling structure having a self-elevating equipment floor on which is mounted a cantilever floor-mount mast, wherein the mechanical arrangement is usable both for large and small drilling assemblies.